Function Keys

I have always loved how the function keys on my Powerbook are set up to control brightness/volume/expose/dashboard, etc. However, now I am doing some extensive work with Excel and need the function keys to, well, function normally to be able to use them for certain shortcuts.

Is there an easy way to disable the brightness/volume/expose/dashboard, etc. while using Excel and then change them back when I'm done. I understand I can do each one individually, but would like to shut them all off and on easily.

Any suggestions?

 

Thank you!